Subject of the invention is a device enabling the revolutionary speed between two rotating parts, such as the supports of a vehicle wheel, to be measured.
It is known that at present special control circuits known as ABS are installed on vehicles, the purpose of which is to prevent the wheels from blocking during the braking phase. The measurement systems presently being used are realized by means of common basic components such as: phonic ring, measurement sensor, an on-board computer and an oleodynamic gearcase.
Typically a phonic ring is a toothed ring mounted on the rotating part to keep under control while the sensor either passive or active, is installed on the stationary part of the frame at a certain distance from the opposite toothed area of the phonic ring.
The electric signals from the sensors are sent to the on-board computer of the ABS system measuring the speed difference between wheels.
Passive sensors, in use at present, are reluctance-change sensors and require no feed; however, these sensors must necessarily be mounted outside the bearing and are exposed to possible shocks, polluting agents and other possible dangers.
In particular this sensor can be damaged by metal particles (wear) from the brakes, which are close to the sensors and by high temperatures, developed by brake discs; they also need to be duly calibrated by the user during the assembly phase.
Active sensors presently in use are typically inductive consisting in a small coil fed by an oscillating circuit or by elements sensitive to magnetic field variations (Hall effect).
These sensors can be housed inside wheel bearings but they nevertheless need input from the outside.